UPnP daemon

A daemon for continuously opening ports via UPnP.

Motivation

There are quite some programs out there that need certain network ports to be open to work properly, but do not provide the capability for opening them automatically via UPnP. Sure, one could always argue about the security implications that come with UPnP, but if you are willing to take the risk, it is just annoying, that for example your webserver is not reachable from the internet, because you forgot to open port 80, or your router rebooted and cleared the table of open ports. Or your machine does for whatever reason not have a static IP address, so you cannot add a consistent port mapping.

Because of this frustration, I created upnp-daemon, a small service written in Rust, that will periodically check a file with your defined port mappings and send them to your router. The main usage will be that you start it once and let it run as a background service forever. The file with the port mappings will be newly read in on each iteration, so you can add new mappings on the fly.

Installation

upnp-daemon can be installed easily through Cargo via crates.io:

cargo install --locked upnp-daemon

Please note that the --locked flag is necessary here to have the exact same dependencies as when the application was tagged and tested. Without it, you might get more up-to-date versions of dependencies, but you have the risk of undefined and unexpected behavior if the dependencies changed some functionalities. The application might even fail to build if the public API of a dependency changed too much.

Alternatively, pre-built binaries can be downloaded from the GitHub releases page.

Usage

Usage: upnp-daemon [OPTIONS] --file <FILE>

Options:
  -f, --file <FILE>                    The file (or "-" for stdin) with the port descriptions
      --format <FORMAT>                The format of the configuration file [default: csv] [possible values: csv, json]
  -d, --csv-delimiter <CSV_DELIMITER>  Field delimiter when using CSV files [default: ;]
  -F, --foreground                     Run in foreground instead of forking to background
  -1, --oneshot                        Run just one time instead of continuously
  -n, --interval <INTERVAL>            Specify update interval in seconds [default: 60]
      --close-ports-on-exit            Close specified ports on program exit
      --only-close-ports               Only close specified ports and exit
      --pid-file <PID_FILE>            Absolute path to PID file for daemon mode [default: /tmp/upnp-daemon.pid]
  -h, --help                           Print help
  -V, --version                        Print version

In the most basic case, a call might look like so:

upnp-daemon --file ports.csv

This will start a background process (daemon) that reads in port mappings from a CSV file (see config file format) every minute and ask the appropriate routers to open those ports.

The PID of the process will be written to /tmp/upnp-daemon.pid by default and locked exclusively, so that only one instance is running at a time. To quit it, kill the PID that is written in this file.

Bash can do it like so:

kill $(</tmp/upnp-daemon.pid)

If you want the PID to be written to another file, maybe because you want to have multiple running instances intentionally, or because your daemon watcher expects the file in another place, you can use the --pid-file option to choose your own file path. Due to technical reasons, this PID file must always be given as an absolute path. Please be aware that this application does not create folders, so the parent folder of the PID file needs to exist beforehand. Also, of course, the user running the application needs to have write permission to the folder.

A note to Windows users: The daemonize library that is used to send this program to the background, does only work on Unix like systems. You can still install and use the program on Windows, but it will behave as if you started it with the --foreground option (see below). Therefore, you will also not see the --pid-file option on Windows since it has no use there.

Reading from standard input

Depending on the actual use case, there might be the need to read in the ports configuration from stdin. In this case, you can give the pseudo filename "-", like so:

generate-configuration | upnp-daemon --file -

The configuration generated by the imaginary generate-configuration needs to have the same format as described in chapter config file format.

Note: If you actually want to read in a file with the name -, give it as an absolute or relative file path, like so:

upnp-daemon --file ./-

Foreground Operation

Some service monitors expect services to start in the foreground, so they can handle them with their own custom functions. For this use case, you can use the foreground flag, like so:

upnp-daemon --foreground --file ports.csv

This will leave the program running in the foreground. You can terminate it by issuing a SIGINT (Ctrl-C), for example.

A note to Windows users: This option flag does not exist in the Windows version of this program. Instead, foreground operation is the default operation mode, since due to technical limitations, it cannot be sent to the background there.

Oneshot Mode

If you just want to test your configuration, without letting the daemon run forever, you can use the oneshot flag, like so:

upnp-daemon --foreground --oneshot --file ports.csv

You could of course leave off the foreground flag, but then you will not know when the process has finished, which could take some time, depending on the size of the mapping file.

Closing Ports

If you want to close your opened ports when the program exits, you can use the close-ports-on-exit flag, like so:

upnp-daemon --close-ports-on-exit --file ports.csv

If the program later terminates, either by using the kill command or by sending a SIGINT in foreground mode, the currently defined ports in the configuration file will be closed. Errors will be logged, but are not fatal, so they will not cause the program to panic. Those errors might arise, for example, when a port has not been opened in the first place.

If you just want to close all defined ports, without even running the main program, you can use the --only-close-ports flag, like so:

upnp-daemon --foreground --only-close-ports --file ports.csv

The foreground flag here is optional, but it is useful if you need to know when all ports have been closed, since the program only terminates then.

Logging

If you want to activate logging to have a better understanding what the program does under the hood, you need to set the environment variable RUST_LOG, like so:

RUST_LOG=info upnp-daemon --foreground --file ports.csv

To make the logger even more verbose, try to set the log level to debug:

RUST_LOG=debug upnp-daemon --foreground --file ports.csv

Please note that it does not make sense to activate logging without using foreground, since the output (stdout as well as stderr) will not be saved in daemon mode. This might change in a future release.

Config File Format

The config file can be given as either CSV (default for now) or JSON (with --format json). The names and contents of the fields are always the same.

CSV

The format of the port mapping file is a simple CSV file, like the following example:

address;port;protocol;duration;comment
192.168.0.10;12345;UDP;60;Test 1
;12346;TCP;60;Test 2

Please note that the first line is mandatory at the moment, it is needed to accurately map the fields to the internal options.

With the --csv-delimiter option, you can choose an arbitrary character to be used as a field delimiter in your CSV file. By default, we use the semicolon, but if you instead prefer a usual comma, you can just say so with --csv-delimiter ','.

Please be aware that your shell might interpret the delimiter (for example, the semicolon is used in bash to separate two commands), so be sure to correctly escape it.

JSON

A config file in JSON format with the above contents could look like this:

[
  {
    "address": "192.168.0.10",
    "port": 12345,
    "protocol": "UDP",
    "duration": 60,
    "comment": "Test 1"
  },
  {
    "address": null,
    "port": 12346,
    "protocol": "TCP",
    "duration": 60,
    "comment": "Test 2"
  }
]

The line breaks and indentations are just for readability, you can format it any way you like. You can even go as far and feed in a single line, as long as it is a valid JSON array with all required fields in it.

Since address is null in the second entry, it can also be left out completely if you prefer. Also, any key that is not documented below will be silently ignored, so you might use them as internal comments for yourself. So a config might also look like:

[
  {
    "rationale": "This port is needed for an awesome application!",
    "may-be-deleted": false,
    "port": 12347,
    "protocol": "TCP",
    "duration": 60,
    "comment": "Test 3"
  }
]

The keys rationale and may-be-deleted will be ignored by the daemon.

Also, please note that even if you want to add just one port mapping, you need to specify a JSON array.

Fields

• address

  The IP address for which the port mapping should be added. This field can be empty, in which case every connected interface will be tried, until one gateway reports success. Useful if the IP address is dynamic and not consistent over reboots.

  Fill in an IP address if you want to add a port mapping for a foreign device, or if you know your machine's address and want to slightly speed up the process.

  You can also enter the IP address in CIDR notation. In that case, the IP range is checked against all connected interfaces and only matching ones are considered. This is useful if you don't know your current IP address (or it might change from time to time), but you know the DHCP configuration of your router.

  Such an IP address might be 192.168.0.10 or 192.168.0.0/24 or even 192.168.0.

  More examples can be found in the responsible library's documentation: https://docs.rs/cidr-utils/0.5.10/cidr_utils/index.html

• port

  The port number to open for the given IP address. Note that upnp-daemon is greedy at the moment, if a port mapping is already in place, it will be deleted and re-added with the given IP address. This might be configurable in a future release.

• protocol

  The protocol for which the given port will be opened. Possible values are UDP and TCP.

• duration

  The lease duration for the port mapping in seconds. Please note that some UPnP capable routers might choose to ignore this value, so do not exclusively rely on this.

• comment

  A comment about the reason for the port mapping. Will be stored together with the mapping in the router.